Cell lineage heterogeneity in blast crisis of chronic myeloid leukaemia

Cancer stem cells in basic science and in translational oncology: can we translate into clinical application?

Since their description and identification in leukemias and solid tumors, cancer stem cells (CSC) have been the subject of intensive research in translational oncology. Indeed, recent advances have led to the identification of CSC markers, CSC targets, and the preclinical and clinical evaluation of the CSC-eradicating (curative) potential of various drugs. However, although diverse CSC markers and targets have been identified, several questions remain, such as the origin and evolution of CSC, mechanisms underlying resistance of CSC against various targeted drugs, and the biochemical basis and function of stroma cell-CSC interactions in the so-called ‘stem cell niche.’ Additional aspects that have to be taken into account when considering CSC elimination as primary treatment-goal are the genomic plasticity and extensive subclone formation of CSC. Notably, various cell fractions with different combinations of molecular aberrations and varying proliferative potential may display CSC function in a given neoplasm, and the related molecular complexity of the genome in CSC subsets is considered to contribute essentially to disease evolution and acquired drug resistance. In the current article, we discuss new developments in the field of CSC research and whether these new concepts can be exploited in clinical practice in the future.

Treatment selection after imatinib resistance in chronic myeloid leukemia

Chronic myeloid leukemia (CML) is a progressive and often fatal malignancy of the blood. The harbinger of CML is a chromosomal translocation that results in the synthesis of the BCR-ABL fusion protein, a constitutively active tyrosine kinase. The advent of imatinib, an inhibitor targeted specifically for BCR-ABL, represented a significant medical advance in CML therapy. However, patients with CML can exhibit varying responses to first-line treatment with imatinib. While most patients respond to treatment, some may experience a loss of response or require treatment discontinuation due to toxicity. Frequent monitoring for resistance or intolerance is a requirement for recognition of suboptimal response. Mutational analysis of the patient's BCR-ABL alleles is also informative and may be predictive of a response to therapy. Published physician guidelines have highlighted these recommendations, but it is not clear if these guidelines are universally followed. One option in patients showing poor response to standard-dose imatinib of 400 mg is to escalate the dose. However, this option should be reserved for patients with minimal disease burden. Clinically available options mainly include second-generation tyrosine kinase inhibitors, such as dasatinib and nilotinib. Allogenic stem cell transplantations (for eligible patients) also should be considered. The disease and patient characteristics at the time of imatinib failure should be evaluated before choosing second-line therapy to optimize the therapeutic benefit without unnecessary delay.

p210(BCR-ABL) reprograms transformed and normal human megakaryocytic progenitor cells into erythroid cells and suppresses FLI-1 transcription

The BCR-ABL oncoprotein exhibits deregulated protein tyrosine kinase activity and is implicated in the pathogenesis of Philadelphia chromosome (Ph)-positive human leukemias. Here, we report that ectopic expression of p210(BCR-ABL) in the megakaryoblastic Mo7e cell line and in primary human CD34(+) progenitors trigger erythroid differentiation at the expense of megakaryocyte (MK) differentiation. Clonal culture of purified CD41(+)CD42(-) cells, a population highly enriched in MK progenitors, combined with the conditional expression of p210(BCR-ABL) tyrosine kinase activity by imatinib identified a true lineage reprogramming. In both Mo7e or CD41(+)CD42(-) cells transduced with p210(BCR-ABL), lineage switching was associated with a downregulation of the friend leukemia Integration 1 (FLI-1) transcription factor. Re-expression of FLI-1 in p210(BCR-ABL)-transduced Mo7e cells rescued the megakaryoblastic phenotype. Altogether, these results demonstrate that alteration of signal transduction via p210(BCR-ABL) reprograms MK cells into erythroid cells by a downregulation of FLI-1. In addition, our findings underscore the role of kinases in lineage choice and infidelity in pathology and suggest that downregulation of FLI-1 may have important implications in CML pathogenesis.

Myeloperoxidase cytochemical negativity: an unexpected but intrinsic property of blasts of all phases of chronic myeloid leukemia

Myeloperoxidase (MPO) cytochemical activity, recognized as a very important hallmark of myeloblasts, is generally negative in chronic myeloid leukemia (CML) blast crisis (BC). Because this finding is unexpected, being not in keeping with the myeloproliferative nature of CML, we tried to ascertain if MPO cytochemical negativity could be an intrinsic property of blasts of CML and hence present in the preblastic phases as well. Myeloperoxidase cytochemistry of peripheral blood blasts in 161 cases of CML, including 103 in chronic phase (CP) and 29 each in accelerated phase (AP) and BC, was assessed and compared with that of 30 cases of acute myeloid leukemia, AML-M2. Blasts of 97 (94.2%) of 103 cases of CP, 28 (96.6%) of 29 cases of AP, and 22 (75.9%) of 29 cases of BC were negative for MPO (<3% MPO-positive blasts). Compared with the strong MPO positivity, both in terms of intensity and proportion, in the AML-M2 cases, the positivity in the CML cases was generally weak and was seen in a small number of blasts (5-15%), except in one case of BC with 20% positive blasts. Absence or, at times, weak MPO cytochemical activity is an intrinsic property of blasts of all phases of CML, and use of the term myeloblast in CML should be understood to refer to a cell with this property. This also explains why MPO cytochemistry, despite its high reputation as a myeloid-lineage marker, generally does not help in CML BC. CML BC should therefore be considered as a possible diagnosis along with acute lymphoblastic leukemia, AML-M0, AML-M7, etc., in the setting of MPO-negative blasts. Similarity between MPO expression pattern in CML, i.e., negative in blasts and positive in the more mature cells, and that during maturation of normal myeloid series of cells shows the deranged myelopoiesis of CML to be undisturbed at least with respect to MPO expression. There is need for a more comprehensive study of blasts of preblastic phases.

Chronic myeloid leukemia: pathophysiology, diagnostic parameters, and current treatment concepts

Chronic myeloid leukemia (CML) is a stem cell disease characterized by excessive accumulation of clonal myeloid (precursor) cells in hematopoietic tissues. CML cells display the translocation t(9; 22) that creates the bcr/abl oncogene. The respective oncoprotein (= BCR/ABL) exhibits constitutive tyrosine kinase activity and promotes growth and survival in CML cells. Clinically, CML can be divided into three phases: the chronic phase (CP), the accelerated phase (AP), and the blast phase (BP) that resembles acute leukemia. Progression to AP and BP is associated with occurrence of additional genetic defects that cooperate with bcr/abl in leukemogenesis and lead to resistance against antileukemic drugs. The prognosis in CML is variable depending on the phase of disease, age, and response to therapy. The only curative approach available to date is stem cell transplantation. For those who cannot be transplanted, the BCR/ABL tyrosine kinase inhibitor STI571 (Glivec, Imatinib), interferon-alpha (with or without ARAC), or other cytoreductive drugs are prescribed. Currently available data show that STI571 is a superior compound compared to other drugs in producing complete cytogenetic and molecular responses. However, despite superior initial data and high expectations for an effect on survival, long term results are not available so far, and resistance against STI571 has been reported. Forthcoming strategies are therefore attempting to prevent or counteract STI571 resistance by co-administration of other antileukemic drugs. Whether these strategies will lead to curative drug therapy in CML in the future remains at present unknown.

Therapeutic strategies for chronic myeloid leukemia in the chronic (stable) phase

During the last four decades, the optimal first-line treatment for chronic myeloid leukemia (CML) in chronic (stable) phase has progressed from alkylating agents, to hydroxyurea (HU), and then to interferon-alfa (IFN-alpha). Treatment for younger patients with suitable donors also includes allogeneic stem cell transplantation, which offers the chance of prolonged leukemia-free survival to about 20% of all CML patients and is the only certain approach to cure. Recently, three phase II studies of imatinib mesylate (STI571), a new inhibitor specific for tyrosine kinase of the Bcr-Abl oncoprotein, have been reported. They led the Food and Drug Administration (FDA) to approve use of this agent to treat CML patients following failure of or withdrawal from IFN-alpha. The advent of imatinib also led to a reassessment of the role of allogeneic transplantation. This article reviews evidence for the safety and efficacy of imatinib and allogeneic stem cell transplantation and suggests strategic approaches to treatment in the new era of tyrosine kinase inhibition.

Double Ph-positive megakaryoblastic transformation of chronic myeloid leukemia

A 64-yr-old Japanese man presented with mild anemia, leukocytosis, and thrombocytosis in November 1999. A diagnosis of chronic myeloid leukemia was made with a positive Ph chromosome, and interferon alpha treatment was started, 6 million units a day. Two years later, in October 2001, the patient developed leukocytosis, an increased LDH level, and large blasts with basophilic cytoplasm with cytoplasmic projections appeared in the peripheral blood. Bone marrow aspiration revealed increased blasts (59.6%). These blasts were negative on peroxidase stain, positive on acid phosphatase, and weakly positive on alpha naphthyl butyrate esterase stain and periodic acid-Schiff stain. Immunohistochemical staining with monoclonal antibodies revealed that these blasts were strongly positive with anti-CD41 (glycoprotein IIb/IIIa), weakly positive with CD7, CD33, and CD34, and negative with other monoclonal antibodies. A diagnosis of megakaryoblastic transformation from chronic myeloid leukemia was therefore made. Two-color fluorescence in situ hybridization (FISH) for portions of the major-bcr and abl genes from bone marrow cells revealed two fused signals in 90.6% and one fused signal in 5.8% of 106 cells. A cytogenetic study revealed that bone marrow cells were 69, XYY, +6, -7, +8, -9, t(9;22)(q34;q11), +11, +13, -15, -16, dic(17;18)(p11;p11), -18, +19, +21, der(22)t(9;22) in six of nine examined cells. These findings confirmed that these megakaryoblasts originated from megakaryocytes of the chronic myeloid leukemia clone.

Peripheral blood findings in chronic myeloproliferative disorders

Chronic myeloproliferative disorders are now frequently detected on routine total blood count. A careful analysis of PB smears allows the diagnosis in many cases, and helps to classify most of them. The peripheral blood parameters may be of prognostic value, especially in AMM. During the follow-up of CMPD, modifications of the PB are of great interest to detect an evolution toward a myelofibrosis or a blastic phase.

What can we learn from leukemia as for the process of lineage commitment in hematopoiesis?

Most contemporary models of hematopoiesis assume lineage fidelity of early progenitor cells. Along with this concept normal hematopoietic cells and the majority of leukemias express exclusively myeloid or lymphoid specific antigens. On the other hand, growing evidence exists challenging the lineage fidelity model. Chronic myeloid leukemia (CML) in the blast crisis may switch to acute lymphoblastic leukemia (ALL) and as a result of the chemotherapy ALL may converse to acute myeloid leukemia (AML). Furthermore, a substantial portion of leukemia cases, named acute mixed-lineage leukemia (AMLL), show simultaneous expression of both myeloid and lymphoid antigens. Immunoglobulin (Ig) and T-cell receptor (TCR) gene rearrangements, correlating with myeloid-lymphoid immunophenotype in AMLL, support the hypothesis of lineage infidelity of early progenitor cells, rather than the aberrant antigen expression. Based on a detailed characterization of AMLL we present a modified model of a "common myeloid/lymphoid progenitor cell". This hypothetical very early hematopoietic progenitor cell shows a transient expression of myeloid and B- or T-lymphoid antigen and may also have rearranged its Ig and/or TCR genes. Subsequently, myeloid or lymphoid markers are downregulated and the hematopoietic cell enters either myeloid, T-lymphoid or B-lymphoid differentiation pathway.

Nodal T cell blast crisis in chronic myeloid leukemia

We report the case of a 54 year old male with an original diagnosis of chronic myeloid leukemia (CML) who developed a nodal T cell blast crisis (BC) while he was in a complete hematological remission (CR). We describe the clinical presentation and the histological, immunophenotypic and molecular characterization of the lymph node blast cells. Our case, together with other rare similar reports in the literature, argue that a T cell nodal blast crisis of CML resembles the presentation of a T-cell non-Hodgkin's lymphoma.

CD56+ blastic transformation of chronic myeloid leukemia involving the skin

We report on two patients with chronic myeloid leukemia (CML) who presented blastic transformation involving the skin, with leukemic infiltrates showing unusual morphologic and immunohistologic characteristics. Both patients were elderly men with a 36-month and a 40-month history of CML, respectively. They presented with disseminated, reddish to violaceous papules and plaques (case 1), and with localized reddish nodules on the left temporal area (case 2). Concurrent features of blastic transformation in the bone marrow were observed in one patient (case 1). Histopathologic examination of skin lesions revealed similar features in both cases. There was a moderate to dense dermal infiltrate composed mainly of medium-sized atypical mononuclear myeloid precursor cells with only few relatively well-differentiated cells of the granulocytic series. Histochemical staining for naphthol-ASD-chloroacetate esterase revealed strong positivity (>50% of neoplastic cells) in case 2 and only scattered positivity (< 10% of neoplastic cells) in case 1. Immunohistologic analysis performed on paraffin-embedded sections showed in both cases variable reactivity of neoplastic cells for leucocyte common antigen (CD45), lysozyme, myeloperoxidase, CD11c, CD15, CD43, CD66, CD68, HLA-DR, and the neural cell adhesion molecule (NCAM) CD56. A negative reaction was observed for CD3, CD34, and TdT. The immunohistologic findings were remarkably similar to those reported for acute myeloid leukemia (AML) with monocytic differentiation (French-American-British [FAB] classification, subtype M4). Examination of blasts from the bone marrow performed in one patient (case 1) revealed a similar phenotype also with CD56 expression. In conclusion, our observations show that specific cutaneous infiltrates in CML may show morphologic and immunohistochemical characteristics similar to those observed in AML with monocytic differentiation. Moreover, specific cutaneous manifestations of CML may express CD56.

Atypical chronic myeloid leukemia with der(20)t(17;20)(q21;q13)

We present a case of atypical chronic myeloid leukemia that developed blastic transformation four months after initial presentation, with the blast cells showing multilineage antigen expression. A novel karyotypic abnormality, der(20)t(17;20)(q21;q13), was found in bone marrow cells at diagnosis. The potential role of such an aberration in leukemogenesis is discussed.

CD7 expression on CD34+ cells from chronic myeloid leukaemia in chronic phase

Thirty-seven patients with chronic phase chronic myeloid leukaemia and fourteen healthy controls have been evaluated for lineage differentiation with immunological markers on purified bone marrow CD34 positive cells by multiparameter flow cytometry. The myeloid-associated antigen CD33 and the stem cell factor receptor (CD117, c-kit) was expressed by 82.3% and 73.5% on CP-CML patients and by 57% and 57.5% on healthy donors, respectively (P < 0.005). CD34+/CD19+ or CD34+/CD10+ B-lymphoid cell population represented 9. 1% and 10.7% of the CD34+ cells in CML whereas in normal controls this subpopulation was expressed by 27.9% and 30.4% of the CD34+ cells, respectively (P< 0.005). The T-lineage associated markers (CD7 and CD2) were detected on a minor population of CD34+ BM cells of healthy controls (mean, 3.6% and 4.6%, respectively). The CD2 positive cells represented 1.5% of the CD34+ cells in CML patients. CP-CML patients co-expressed the CD7 antigen on a mean of 32.6% of the CD34+ BM cells. Moreover, 93% of this CD34/CD7 double positive subpopulation co-expressed CD33 antigen in CML patients. Co-expression of CD7 on CD34+ cells was induced to decrease significantly after short-term in vitro culture with the differentiation-inducing agent phorbol ester (PMA) and with a combination of cytokines (stem-cell factor, interleukin-3 and granulocyte colony-stimulating factor). In conclusion, a high co-expression of CD7 antigen is demonstrated on CD34+ cells of chronic phase-chronic myeloid leukaemia patients. The loss of CD7 marker following incubation with PMA and cytokines suggests that this antigen is expressed transiently in early myeloid leukaemic CML haemopoiesis.

'Lymphoid' blast crisis of chronic myeloid leukaemia is associated with distinct clinicohaematological features

It has been suggested that in blast crisis (BC) of chronic myeloid leukaemia (CML) the clinical and laboratory features of patients with 'lymphoid' phenotype differ from those of patients with non-lymphoid BC. In order to assess any differences, 97 patients consecutively diagnosed with BC that followed a known chronic phase of CML were analysed. 19 patients had 'lymphoid' BC: in 17 the blasts expressed a B-lineage phenotype: in the remaining two they corresponded to T lymphoblasts. Four cases of B-lineage phenotype BC were considered as biphenotypic, due to the co-expression of myeloperoxidase and one or two other myeloid markers (CD33, CD13 and CD68) on the blast cells; in the other six cases of B-lineage BC the blasts expressed one or both of the myeloid markers CD33 (n = 4) and CD13 (n = 3). Patients with 'lymphoid' BC seldom had an accelerated phase prior to BC (1/19 v 36/78 with non-lymphoid BC, P = 0.002), had less frequent splenomegaly (9/19 v 59/78, P = 0.03) and hepatomegaly (5/19 v 45/78, P = 0.02) and showed a higher degree of marrow blast infiltration (mean value 74 +/- 24% v 38 +/- 23%, P < 0.0001), lesser blood basophilia (2.2 +/- 2.5% v 8.2 +/- 7.8%, P < 0.0001), and higher serum albumin levels (P = 0.001) than those with non-lymphoid BC. 13 patients with 'lymphoid' BC (68.4%) showed a favourable response to chemotherapy regimens including vincristine and prednisone and, overall, 'lymphoid' BC patients survived significantly longer than the remainder (median survival 12 months v 4.7 months, P = 0.006). These results indicate that 'lymphoid' BC of CML has a distinct clinicohaematological profile and confirm the better prognosis of such patients.

Burkitt-like blast crisis in chronic myeloid leukemia

A case of Burkitt-like blast crisis in a patient with chronic myelocytic leukaemia (CML) is presented. To our knowledge, this is the first such case recorded to date. The patient had a useful response to combination chemotherapy.

Immunophenotype and ultrastructural studies in blast crisis of chronic myeloid leukemia

Thirty-four patients with chronic myeloid leukemia in blast crisis (CML-BC) were evaluated for lineage differentiation with immunological markers and the presence of ultrastructural peroxidase. Eighteen (52.9%) were found to have myeloid blast crisis. Cytochemically, myeloperoxidase (MPO) could be detected only in six patients on light microscopy while in the remaining 12 patients, myeloid differentiation was confirmed only by demonstration of MPO either at ultrastructural level or by the reactivity with anti myeloperoxidase (anti MPO) antibody. Six (17.6%) had lymphoid blast crisis as identified by lymphoid specific markers (CD19; CD10; CD7; CD4) along with the absence of myeloid markers. Heterogenous blast cell populations with mixed lineage differentiation were seen in 4 (11.7%) patients. These cases showed both lymphoid (CD19, CD10) and myeloid (anti MPO and ultrastructural MPO) characteristics. A single case of megakaryoblastic blast crisis was identified with positivity for CD41 and CD42 along with the presence of platelet peroxidase at the ultrastructural level. Five cases (14%) of CML blast crisis remained unclassifiable. These results suggest that blast crisis in CML show an arrest of differentiation at an early stage when compared to de novo acute leukemias. This is particularly evident from the fact that MPO could only be demonstrated ultrastructurally or with anti MPO antibody in the majority of patients with myeloid differentiation. It is expected that utilisation of molecular studies including immunoglobulin and T-cell receptor gene rearrangement and m-RNA expression for myeloperoxidase will provide a better insight into the level of differentiation for the presently unclassifiable cases of CML-blast crisis.

Platelet derived growth factor expression, myelofibrosis and chronic myelogenous leukemia

CML is often associated with myelofibrosis, and fibrosis in the accelerated phase is one of the diagnostic criteria for this accelerated phase. In this review, the mechanism of myelofibrosis associated with CML is discussed with emphasis on the cell origin of the production and release of platelet derived growth factor (PDGF) and its interaction with marrow fibroblasts. In the initial stage of myelofibrosis in chronic phase CML, atypical small megakaryocytes might leak PDGF, possibly PDGF-AB, together with other growth factors. As the clinical phase of the disease progresses to accelerated or blastic phase, a larger quantity of PDGF-AB or PDGF-BB might be secreted from blastic cells with myeloid phenotype. In addition some fibroblasts may be attracted by the PDGF and proliferate, and deposit collagen as well as fibronectin in the bone marrow stroma.

Cytogenetic and immunogenotypic alterations of blast crisis cells in chronic myelogenous leukemia independently linked to immunophenotypic expression

Chronic myelogenous leukemia (CML) is a disease of the hematopoietic stem cells, which can differentiate into either B-lymphoid or myeloid cells, because most of them develop either lymphoid or myeloid blast crisis. Immunophenotypic, genotypic, and cytogenetic analyses of 22 patients (24 episodes) with Philadelphia (Ph) positive CML in blast crisis were performed to determine the genetic alterations of the blast crisis cells. In B-lymphoid blast crisis, all the five patients had immunoglobulin heavy-chain (IgH) rearrangements and most of them showed normal karyotypes. Among the five patients, T-cell receptor (TCR) genes were rearranged at the following occurrence rates: 20% in TCR-beta, 60% in TCR-gamma, and 40% in TCR-delta chain genes. A high incidence of additional chromosome changes was noted in patients with B-lymphoid/myeloid-mixed blast crisis, but about 80% of them had rearranged IgH and about 40% had TCR rearrangements. In contrast, most of the patients with non-lymphoid blast crisis showed further chromosomal abnormalities, including +8, +19, i(17q), and double Ph, and most of them had germline configurations of IgH and TCR-gamma chain genes. Notably, only one patient (dual lymphoid and myelomegakaryoblast crisis) in this group exhibited IgH rearrangement, and TCR-beta and TCR-delta rearrangements were also rarely noted. Rearrangement of the IgH gene in CML blast crisis might be linked to expression of lymphoid markers, especially CD19.

Tetrasomy 8 in acute monoblastic leukemia (AML-M5a) with myelosarcomatosis of the skin

We report a new case with isolated tetrasomy 8, an 82-year-old female patient in whom multiple disseminated nodular skin infiltrations up to 5 cm in diameter preceded acute monoblastic leukemia (AML-M5a). Despite an initial response to chemotherapy and radiotherapy, the patient died 1 year after diagnosis of relapsed leukemia. To assess the size of the tetrasomic clone, fluorescence in situ hybridization (FISH) analysis with a centromere-specific chromosome 8 probe was performed. Seventy percent of interphase cells showed four signals and 22% showed three signals. Because this trisomic clone was not detected by conventional cytogenetics, tetrasomic cells may have a proliferation advantage in vitro. Whether tetrasomy 8 arises from a simultaneous mitotic nondisjunction of both chromosomes 8 during one cell division or evolves secondarily from trisomy 8 through a second mitotic error is not known. Alternatively, trisomy 8 may originate from tetrasomy 8 by loss of one chromosome 8.

Comparison of clinical and biologic features between myeloid and lymphoid transformation of Philadelphia chromosome positive chronic myeloid leukemia

Analysis of clinical and biologic features of chronic myeloid leukemia (CML) in blast crisis (BC) was performed on 36 patients: 25 had myeloid and 11 had lymphoid transformation. The median duration from diagnosis to onset of BC was significantly shorter in patients with lymphoid BC (6 months) than in those with myeloid BC (41 months). Patients in lymphoid transformation showed better response to therapy and had a significantly longer median survival time after BC than patients with myeloid transformation (56% vs 0% and 10 months vs 4 months, respectively). The leukemic cells from all the patients with lymphoid BC showed B-cell immunophenotype, confirmed by the presence of immunoglobulin (Ig) heavy chain gene rearrangements in the five patients studied. Two of the eight patients with complete marker study expressed myeloid-associated antigens on the blasts. A high incidence of CD7 expression (7/17 or 41%) was found in patients with myeloid BC, but none of the patients who had DNA analysis showed rearrangement of T-cell receptor beta chain gene. Chromosomal abnormalities +8, +19, +21, and i(17q) were detected only in the patients with myeloid BC but not in those with lymphoid BC. Combined analysis of the patients in this series and those reported previously has revealed a statistically significant difference in the distribution of bcr breakpoints between myeloid and lymphoid BC: the bcr breakpoints in more than half of the patients with myeloid crisis were mapped to Zone 2 while those in patients with lymphoid crisis occurred most frequently in Zone 3.

Acute lymphoid leukemias following either a previous chronic myelogenous leukemia or myelodysplastic syndrome: phenotypic and genomic differences

We have analyzed the immunological and genomic characteristics of the lymphoid blast cells present in secondary lymphoid leukemias following either a previous chronic myelogenous leukemia (CML) or myelodysplastic syndrome (MDS). Twenty-one of 107 secondary leukemias analyzed displayed a lymphoid phenotype (15 after a CML and 6 after a MDS). Most of the lymphoid blast crises of CML (73%) correspond to pure lymphoid transformation, all of them having a common acute lymphoblastic leukemia (ALL) phenotype (CD10+). By contrast, in all MDS cases, lymphoid blast cells coexisted with another myeloid component (hybrid leukemias) and showed an early B phenotype. IgH and TCR-gamma gene rearrangements were detected in the CML-lymphoid blast crisis (86% of cases) more frequently than in the MDS transformations (33%). The TCR-beta gene was in germ line configuration in all cases while TCR-delta gene rearrangements were detected in four cases, all of them corresponding to a previous diagnosis of CML. These results show the existence of both immunophenotypic and genomic differences between the lymphoid transformations of either CML or MDS, which could reflect differences at the stage of maturation of the target cell in these transformations.

Immunophenotypic characterisation of acute leukaemia after polycythemia vera

AIMS

To analyze the immunophenotype of blast cells in patients with acute leukaemia after polycythemia vera, together with the most relevant clinical and haematological disease characteristics.

METHODS

The immunophenotype was analysed in nine patients by immunofluorescence flow cytometry using a panel of 15 monoclonal antibodies. The DNA content of blast cells was determined using Vindelov's technique.

RESULTS

The most relevant clinical and haematological disease characteristics included: the presence of enlarged spleen and liver by 56% and 67%, respectively; a moderate degree of leucocytosis with thrombocytopenia while haemoglobin was normal in 50% of patients. All patients received alkylating agents or hydroxyurea, or both. Interestingly, the chronic phase in patients receiving this latter drug was shorter. All cases showed a myeloid phenotype, four of them reactive only to early myeloid antigens (CD13/33); in the remaining cases the blast cells displayed granulomonocytic (CD14+, CD15+), erythroid (CD71 ), or megakaryocytic (CD61+, CD41+) markers. Coexpression of lymphoid related antigens (CD7, TdT, or CD19) was also detected. The morphological assessment of blast cells agreed with the immunophenotyping in five out of the nine cases. Blast cells from all six patients analysed displayed a diploid DNA content and the proportion of S-phase cells ranged from 0.4% to 4%.

CONCLUSIONS

These findings suggest a pluripotential stem cell with myeloid commitment as the target cell of acute leukaemia after polycythemia vera.

High incidence of meningeal leukemia in lymphoid blast crisis of chronic myelogenous leukemia

Fifteen patients with lymphoid blast crisis of chronic myelogenous leukemia (LyBC-CML) and five patients with acute lymphoblastic leukemia converting to Philadelphia-positive (Ph+) chronic myeloid leukemia (ALL Ph + CML) were followed. Seven of 15 (46.7%) LyBC-CML patients developed meningeal leukemia within a median period of 6 months (range 2-11 months), while there was no medullary relapse. Five of these responded well to triple intrathecal therapy. In the ALL Ph + CML patients, in spite of central nervous system (CNS) prophylaxis with IT MTX and 18 Gy cranial radiation, two of five patients (40%) experienced meningeal leukemia, one isolated and the other with medullary relapse. The data confirm that LyBC-CML patients experience a high incidence of meningeal leukemia. The role of CNS prophylaxis is not very clear, but its use may delay development and reduce morbidity due to CNS disease.

Inversion of chromosome 16 and bone marrow eosinophilia in a myelomonocytic transformation of chronic myeloid leukemia

We report a case of chronic myeloid leukemia (CML) in myelomonocytic transformation associated with bone marrow (BM) eosinophilia. At diagnosis, all BM cells showed a Ph chromosome. At the time of blastic phase, more than 50% of Ph+ cells had a pericentric inversion of chromosome 16, inv(16)(p13q22). This case confirms that blastic transformation of CML can involve any committed progenitor, and myelomonocytic leukemia with BM eosinophilia is specifically associated with rearrangement of chromosome 16 at band p13 and q22.

Development of acute leukaemia after idiopathic myelofibrosis

AIMS

To determine the characteristics of blastic transformation of idiopathic myelofibrosis.

METHODS

The clinical and haematological features, as well as the morphological characteristics of blast cells, were analysed in nine adults with blast transformation.

RESULTS

Most of the patients were male and had enlarged spleens and livers. Five of the patients had normal platelet counts, while all had pronounced anaemia and a moderate degree of leucocytosis. The duration of the acute phase was usually short: 16 (SD 8) weeks. Most myeloid cell lineages--granulocytic, monocytic, and megakaryocytic--were similarly distributed. One patient also had a hybrid (lymphoid-myeloid) phenotype. The morphological assessment of blast cells agreed with immunophenotyping in five out of the nine cases. The onset of the blastic phase was not related to previous treatment.

CONCLUSIONS

A pluripotential stem cell with preferential myeloid commitment would be the target cell of blast transformation in idiopathic myelofibrosis. Our immunophenotypic data do not support the concept of a preferential association between megakaryocytic lineage and the acute transformation of idiopathic myelofibrosis. The absence of previous treatment in some cases suggests that this kind of evolution is part of the natural history of idiopathic myelofibrosis.

Phenotypic and genotypic switch in Philadelphia-positive, BCR-positive blast crisis of chronic myeloid leukemia

We report a case of Ph1-positive, bcr-positive chronic myeloid leukemia blast crisis (CML-BC) which at presentation showed a mixed myeloid/B-lymphoid immunophenotype along with TdT positivity and, at the molecular level, an oligoclonal rearrangement of the immunoglobulin heavy chain (IgH) gene region. After obtaining a successful remission, at the time of relapse the patient underwent a phenotypic and genotypic switch from mixed to myeloid phenotype, characterized by the loss of the lymphoid markers and TdT expression and by a germline configuration of the IgH gene region. The same bcr rearrangement was, however, found in both phases of the disease, supporting the suggestion of a true phenotypic and genotypic conversion. This report confirms that the neoplastic event in CML may take place at an early multipotent stem-cell level, prior to a well-defined phenotypic and genotypic lineage expression. Moreover, it is suggested that different factors (chemotherapy? growth factors?) may have either eradicated the bcr+/IgH+ clone and promoted the growth of bcr+/IgH- leukemic cells or, alternatively, supported the lymphoid differentiation program and induced a myeloid lineage shift.

Simultaneous occurrence of t(14;18) and t(8;22) common acute lymphoblastic leukemia

A young male patient progressed rapidly from localized abdominal lymph node enlargement to overt acute lymphoblastic leukemia. Despite aggressive treatment, he died of progressive CNS leukemia 5 months after initial presentation. At diagnosis, karyotypic analysis of an abdominal lymph node revealed the coexistence of t(14;18) (q32;q21), specific for follicular lymphoma, and t(8;22) (q24;q11), a variant Burkitt translocation. Such cases might be considered as a model for a general mechanism of tumor progression with cascade-like involvement of oncogenes.

Immune markers in hematologic malignancies

The precise delineation of biologic traits that distinguish normal hematopoietic cells from their malignant counterparts is of fundamental importance in understanding all aspects of hematologic malignancies. An increasingly sophisticated technologic battery has been utilized to dissect out these differences--primarily utilization of monoclonal antibodies, by immunoperoxidase, immunoalkaline phosphatase and flow cytometric techniques. An even more basic understanding of normal and malignant hematopoietic cells has begun to evolve as molecular biology begins to unravel gene misprogramming by Southern and Northern blot analysis and the polymerase chain reaction. These techniques not only help distinguish a normal cell from a malignant one, but characterize the malignant clone as B-lymphoid, T-lymphoid or myeloid and allow further subcategorization within these broad lineages. These distinctions are vital to the entire spectrum of basic and clinical research involving hematologic malignancies and are assuming an increasingly important role in their diagnosis, prognosis and treatment.

Immunophenotypic, genomic and clinical characteristics of blast crisis of chronic myelogenous leukaemia

We have studied phenotypic and clinical features in a consecutive series of 45 patients with chronic myelogenous leukaemia (CML) in blast crisis (BC). In addition, in 22 of these patients we have analysed the genotypic characteristics including immunoglobulin, T-cell receptor (TCR) and major breakpoint cluster region (M-bcr) gene organization. The granulomonocytic and megakaryoblastic lineages are the most commonly involved in these BC of CML (33% and 33% of cases, respectively); only 18% of our cases displayed a lymphoid phenotype. Moreover, both morphological and immunophenotypic studies revealed the frequent coexistence of two or three cell populations, especially when the megakaryoblast component is involved. The lymphoid BC displayed the highest incidence of complete remissions although this was not associated with a longer survival. Only minor differences between the different myeloid subgroups were observed. Immunoglobulin heavy chain (IgH) gene rearrangement was found in five of the six lymphoid BC and in one myeloid BC. Only one case showed k light chain gene rearrangement. In all but one myeloid BC the TCR-beta gene was in germline configuration. The TCR-gamma gene was rearranged in all lymphoid and one myeloid BC, while TCR-delta gene rearrangement was detected in 67% and 16% of the lymphoid and myeloid BC, respectively. Most of the lymphoid BC (4/5) had the M-bcr breakpoint in subregion 3, while the myeloid BC had the breakpoint either in subregion 2 or 3. No differences between the different myeloid phenotypic subgroups were observed in relation to breakpoint.

Disseminated intravascular coagulation and decrease in fibrinogen levels induced by vincristine/prednisolone therapy of lymphoid blast crisis of chronic myeloid leukemia

Therapy with vincristine (2 mg i.v. weekly) and prednisolone (100 mg p.o. daily) caused a decrease in fibrinogen levels in nine patients treated for lymphoid blast crisis LBC) of chronic myeloid leukemia (CML). During the first days of treatment disseminated intravascular coagulation (DIC), evidence by a positive ethanol gelation test, markedly increased thrombin-antithrombin III complex and fibrin-split product D-dimer levels, and a rapid fall in fibrinogen levels was observed in two patients. The induction of DIC in these two patients caused profuse bleeding in one and necessitated substitution therapy with fibrinogen and platelet concentrates. The remaining seven patients revealed no signs of DIC; nevertheless, four of them showed a moderate increase in D-dimer levels after initiation of therapy. In these patients a well-known side effect of long-term steroid therapy, namely a decrease of fibrinogen levels, was observed within the first week of treatment. Fibrinogen levels did not fall below 150 mg/dl and increased after dose reduction from 100 mg/day to 50 mg/day. We conclude from our results that two types of disturbances in fibrinogen metabolism can be observed during vincristine/prednisolone therapy of LBC of CML: (a) a decrease of fibrinogen levels due to a steroid-mediated impairment of liver synthesis, and (b) a rapid fall in fibrinogen levels in the course of DIC, most likely induced by the release of procoagulants from deteriorating blast cells, leading to severe bleeding in selected cases.

Chronic myeloid leukaemia lymphoid blast crisis. Relevance of molecular analysis at the bcr and immunoglobulin heavy chain gene level in monitoring response to therapy and residual disease

Southern blot analyses were performed in sequential DNA samples from 4 patients with Ph' + chronic myeloid leukaemia (CML) who underwent lymphoid or mixed blast crisis (BC). Genomic rearrangements at the breakpoint cluster region (bcr) and immunoglobulin heavy chain (IgH) gene level provided, in these cases, a sensitive and specific evaluation of response to therapy both in terms of blasts and Ph' + cell suppression. Recurrent BC was molecularly characterized in the 4 patients, showing each time identical individual specific DNA rearrangement patterns. Residual blasts were detected in 2 cases during intervening chronic phases by IgH rearrangements. Such findings highlight the specificity of these molecular markers, clearly indicating the failure of ablative therapy in eradicating the neoplastic clone. Finally, molecular and phenotypic identity in individual recurrent BC also suggested, in our cases, a lack of clonal evolution during disease progression.

Mixed blasts crisis following extramedullary involvement with the cytogenetic evidence of clonal evolutions in Philadelphia chromosome-positive chronic myelocytic leukemia

We describe a unique case of a young girl with adult type chronic myelocytic leukemia (CML). Clinically she had an extramedullary blastic crisis (BC) prior to that in peripheral blood and in bone marrow. The blasts were primitive cells and always CD7, CD33, CD34 and HLA DR-positive. During the course of illness the blasts became negative for CD5 and positive for CD41a and for platelet-peroxidase. Additional chromosomal appearances and subsequently clonal evolution were seen during the clinical course. Surface antigen modulation and morphological changes, which were observed by microscopic examination and flow cytometry, were induced by in vitro incubation. Surface antigen modulation was more induced in the presence of phytohemagglutinine-conditioned media (PHA-CM) but the effects of PHA-CM on morphological changes were not clear.

A hypothetical model to explain the 'termination' of chronic myeloid leukemia into blastic crisis

Chronic myeloid leukemia is characterised by two discrete phases, a 'benign' phase which terminates into an 'acute' phase. Various explanations have been given to explain the cause of 'blastic' crisis in CML. But the consistency and regularity with which blast crisis occurs and the irregularity with which the factors which are ascribed to cause it (e.g. additional chromosomal abnormalities, change in bcr/abl rearrangement, etc. occur, suggests that CML-BC is not a stochastic process in the natural history of CML but is predetermined at the time of the first mutation in the stem cell. A hypothetical model is put forward proposing this. Different points supporting the model are discussed. The most important implication of this model would be to provide an insight that should lead to the development of more selective and appropriate treatment strategies for this disease.

Target cell of leukemic transformation in acute megakaryoblastic leukemia

Acute megakaryoblastic leukemia (AMkL) is a newly defined acute leukemia in which the differentiation of proliferating blasts is arrested at the megakaryocytic precursor stage. In order to clarify whether a target cell of leukemic transformation in AMkL is a cell committed to megakaryocytic lineage, or a multipotential stem cell, we examined AMkL patients with regard to: a) the presence of myelodyplastic features in residual erythroid and granulocytic cells, b) coexistence of myeloperoxidase (MPO)-positive blasts with megakaryoblasts, and c) the presence of the same chromosomal abnormality in erythroid and granuloid colony-forming cells as seen in megakaryoblasts. Regarding the former two items, results were compared with those from megakaryoblastic crisis of chronic myelocytic leukemia (CML-MkBC) and transient myeloproliferative disorder in Down syndrome (DS-TMD), which are thought to be multipotential stem cell disorders. Among 18 patients with AMkL, three, all complicating myelofibrosis, had marked myelodysplastic changes of erythroid series and/or granulocytic series. In 4 out of 7 patients with CML-MkBC, 5 out of 8 patients with DS-TMD, and 7 out of 18 patients with AMkL, MPO-positive blasts, even though rare, were observed in addition to PPO-positive blasts. All except one of these patients with AMkL also showed complicating myelofibrosis. In one case of AMkL with myelofibrosis, chromosomal analysis of cultured cells of individual colonies revealed that all the analysable metaphases from both CFU-GM and BFU-E had the same chromosomal abnormality as megakaryoblasts. This study has clarified that a considerable proportion of AMkL cases, particularly those with complicating myelofibrosis or showing acute myelofibrosis, arise against the background of a multipotential stem cell disorder, even if blasts are exclusively megakaryocytic in phenotype.

Rearrangement of immunoglobulin and TCR genes in lymphoid blast crisis of Ph+ chronic myeloid leukaemia

Clonal rearrangements of immunoglobulin heavy chain genes as well as both T cell receptor (TCR) delta and gamma genes were found in four cases of blast crisis of Ph+ chronic myeloid leukaemia with unequivocal B cell precursor (common) immunophenotype. In one case, the TCR beta chain gene was also rearranged. Although the developmental sequence of TCR delta, gamma and beta rearrangements in T lymphocytes appeared to be respected, a full phenotypic effect, characteristic of T cell was not observed in these otherwise typical 'common' blast cells. Cytogenetic analysis ruled out the occurrence of TCR rearrangement due to structural chromosome changes. A high incidence of unexpected TCR gene rearrangements has been previously reported in the de novo 'common' acute lymphoblastic leukaemias (ALL). Our cases of chronic myeloid leukaemia (CML) in lymphoid blast crisis show that genotypic similarities may exist between these two haematological entities.

Natural killer lymphocyte blast crisis of chronic myelogenous leukemia

We describe for the first time a case report documenting a chronic myelogenous leukemia (CML) patient who developed a blast crisis of natural killer (NK) lymphocytes. Many of the blasts exhibited large granular lymphocytic (LGL) morphology. Single parameter immunophenotyping results determined that the granulated as well as the agranulated blast cells were NK lymphocytes (CD45, NKH1, CD2, LEU 17, and CD16 positive; CD3, CD8, and LEU 7 negative). Dual parameter flow cytometric testing also determined that some of the blasts expressed the CD11b and CD11c markers as reported for some types of NK lymphocytes. Approximately 10% of the cells were in the S phase of the cell cycle as determined by a modified Vindelov DNA content analysis test and may theoretically reflect some of those cells expressing CD11b and CD11c. The cells did not express in vitro NK lymphocyte functional activity against a K562 target and therefore similar to other reported cases of presumably immature NK lymphocytic leukemias. The NK lymphocyte blast crisis was successfully treated with vincristine and prednisone. The patient's disease eventually relapsed and transformed to a progenitor stem cell before she died (CD45, 13, CD38, and CD34 positive). The flow cytometric immunophenotyping results contributed significantly as an important adjunct in determining the appropriate diagnosis, helping to select the type of therapy, and monitoring the patient with this unusual type of blast crisis.

Chromosomal characteristics of Ph-positive chronic myelogenous leukemia in transformation. A study of 23 Chinese patients in Taiwan

Cytogenetic study was performed in the past 3 years on 23 Chinese patients with Philadelphia chromosome (Ph) positive chronic myelogenous leukemia (CML) in transformation; seven were in accelerated phase and 16 in acute blast crisis. Chromosomal abnormalities in addition to Ph were found in three (43%) of the patients at accelerated phase and 14 (88%) of the patients at blast crisis. The common nonrandom chromosomal aberrations were double Ph, trisomy 8, trisomy 19, and trisomy 21, which occurred in 47%, 41%, 35%, and 29%, respectively, of the total patients with extra chromosomal abnormalities. Isochromosome for the long arm of chromosome 17 was found in only one patient. In patients with blast crisis, the type of blast cell was characterized through morphologic, cytochemical, and immunocytochemical studies. Eleven cases were classified as myeloid and five as lymphoid transformation. Trisomy 8, 19, and 21 were detected only in patients with myeloid blast crisis. This study also revealed a high incidence of trisomy 21 and a low incidence of i(17q) in Chinese patients with transformation of CML.

Laboratory and clinical applications of monoclonal antibodies for leukemias and non-Hodgkin's lymphomas

Important insights into leukocyte differentiation and the cellular origins of leukemia and lymphoma have been gained through the use of monoclonal antibodies that define cell surface antigens and molecular probes that identify immunoglobulin and T-cell receptor genes. Results of these studies have been combined with markers such as surface membrane and cytoplasmic immunoglobulin on B lymphocytes, sheep erythrocyte receptors on T lymphocytes, and cytochemical stains. After using all of the aforementioned markers, it is now clear that acute lymphoblastic leukemia (ALL) is heterogeneous. Furthermore, monoclonal antibodies that identify B cells, such as the anti-CD20 and anti-CD19 antibodies in combination with studies of immunoglobulin gene rearrangement, have demonstrated that virtually all cases of non-T-ALL are malignancies of B-cell origin. At least six distinct subgroups of non-T-ALL can now be identified. T-ALL is subdivided by the anti-CD7, anti-CD5, and antibodies that separate T lymphocytes subsets into three primary subgroups. Monoclonal antibodies are also useful in the subclassification of non-Hodgkin's lymphoma, and certain distinct markers can be correlated with morphological classification. Although monoclonal antibodies are useful in distinguishing acute myeloid from acute lymphoid leukemias, they have less certain utility in the subclassification of acute myelogenous leukemia (AML). Attempts to subclassify AML by differentiation-associated antigens rather than by the French-American-British (FAB) classification are underway in order to document the potential prognostic utility of surface markers. Therapeutic trials using monoclonal antibodies in leukemia and lymphoma have been reported. Intravenous infusion of unlabeled antibodies is the most widely used method; transient responses have been demonstrated. Antibodies conjugated to radionuclides have been quite successful in localizing tumors of less than 1 cm in some studies. Therapy trials with antibodies conjugated to isotopes, toxins, and drugs have shown promise. Purging of autologous bone marrow with monoclonal antibodies and complement in vitro has been used in ALL and non-Hodgkin's lymphoma; preliminary data suggest that this approach may be an effective therapy and may circumvent many of the obstacles and toxicities associated with in vivo monoclonal antibody infusion.

Analysis of peroxidase negative acute leukemias by monoclonal antibodies: III. Acute lymphoblastic leukemia

Peripheral-blood leukemic cells from 45 patients with peroxidase negative acute lymphoblastic leukemia (ALL), which did not express either myeloid or megakaryocyte-platelet-related cell surface antigens, were analyzed by using monoclonal antibodies capable of recognizing T- or B-cell-associated and/or T- or B-cell-restricted antigens. Numerous subclasses of ALL, including B-cell lineage leukemias and T-cell lineage leukemias, were identified phenotypically and immunophenotypically in an effort to more accurately characterize the heterogeneous ALLs, their states of differentiation, and their relationships to normal B- and T-lymphoid cells. Among the cases studied, only seven (15.6%) were found to have stem cell (undifferentiated) leukemia (Ia+, CD24+, CD9+, CD34+). It is concluded that the use of monoclonal antibodies for the characterization of heterogeneous ALLs improves the specificity of leukemia classification, which may contribute to the selection of more effective forms of therapy for the types of leukemia identified.

Possible cytogenetic distinction between lymphoid and myeloid blast crisis in chronic granulocytic leukemia

This study consists of 25 patients with chronic granulocytic leukemia in blast crisis (BC) or with acute leukemia who had a Ph1 chromosome and one or more other chromosome abnormalities and who were investigated by cytochemistry and immunocytochemistry techniques to determine whether the predominant blasts were myeloid or lymphoid. The disorder was myeloid in 15 patients, lymphoid in 8, and mixed in 2. Among the 15 patients with myeloid disorders, 13 (86.6%) had an additional Ph1 chromosome, i(17q), +8, +19, or some combination of these abnormalities. None of the eight patients with a lymphoid disorder had +8, +19, or i(17q), but one had an additional Ph1 chromosome. Among the eight patients with lymphoid disorders, two had structural abnormalities of chromosome 7 and two were monosomy 7. None of the patients with myeloid disease had a structurally abnormal chromosome 7, but one was monosomy 7. Our findings suggest that the number of chromosomes in an abnormal clone may be unreliable for distinguishing between lymphoid and myeloid BC. Most patients with myeloid disease had only abnormal metaphases, whereas many patients with lymphoid disorders had both normal and abnormal metaphases. This finding may partially explain why many patients with lymphoid BC respond better to treatment than do those with myeloid BC.